Building ASP.NET Core 2.0 preview 2 packages on AppVeyor

I was recently creating a new GitHub project and I wanted to target ASP.NET Core 2.0 preview 2. I like to use AppVeyor for the CI build and for publishing to MyGet/NuGet, as I can typically just copy and paste a single file between projects to get my standard build pipeline. Unfortunately, targeting the latest preview is easier said than done! In this post, I'll show how to update your appveyor.yml file so you can build your .NET Core preview libraries on AppVeyor.

Building .NET Core projects on AppVeyor

If you are targeting a .NET Core SDK version that AppVeyor explicitly supports, then you don't really have to do anything - a simple appveyor.yml file will handle everything for you. For example, the following is a (somewhat abridged) version I use on some of my existing projects:

There's really nothing fancy here, most of this configuration is used to define when AppVeyor should run a build, and how to deploy the NuGet package to NuGet. There's essentially no configuration of the target environment required - the build simply calls the build.ps1 file to restore and build the project.

The tricky part is working out exactly what to run! I couldn't find any official guidance on scripting the install, so I went hunting in some of the Microsoft GitHub repos. In particular I found the JavaScriptServices repo which manually installs .NET Core. The install node at the time of writing (for preview 1) was:

There's a lot of commands in there. Most of it we can copy and paste, but the trickiest point is that download URL - GUIDs, really?

Luckily there's an easy way to find the URL for preview 2 - you can look at the release notes for the version of .NET Core you want to target.

The link you want is the Windows 64-bit SDK binaries. Just right-click, copy the link and paste into the appveyor.yml, to give the final file. The full AppVeyor file from my recent CommonPasswordValidator repository is shown below:

Now when AppVeyor runs, you can see it running the install steps before running the build script:

Using predictable download URLs

Shortly after battling with this issue, I took another look at the JavaScriptServices project, and noticed they'd switched to using nicer URLs for the SDK binaries. Instead of using the horrible GUIDy URLs, you can use zip files stored on an Azure CDN instead. These URLs just require you know the SDK version (including the build number) For example:

It looks like preview 2 is the first to be available at this URL, but as you can see, later builds are also available if you want to work with the bleeding edge builds.

Summary

In this post I showed how you could use the install node of an appveyor.yml file to install ASP.NET Core 2.0 preview 2 into your AppVeyor build pipeline. This lets you target preview versions of .NET Core in your build pipeline, before they're explicitly supported by AppVeyor.